1. Field of the Invention
The present invention relates to a copper alloy material preferably used for an electric conductive material for various kinds of electronic devices and a method of preparing the same.
2. Discussion of Background
There has been well known to use e.g. a brass series alloy or a phosphor bronze series alloy which has been practically used for various fields such as connectors.
As characteristics required for materials for electronic devices, they should have a mechanical strength such as a tensile strength of about 50 kgf/mm.sup.2 as well as the same electric conductivity and anti-corrosion properties as the phosphor bronze. In recent years, however, demands for miniaturization, a high performance and utility in various circumstances are increasing for the electronic, devices, and therefore, materials having accuracy and reliability are required. Further, cost for producing the materials should be low.
As an example of such demands, a material having a high electric conductivity, heat resistance properties and a low sensitivity to a migration phenomenon is required while the electronic devices should be miniaturized and should possess a high performance. Brass which has been used as an alloy for electronic devices has disadvantages of low mechanical strength and a large sensitivity to stress-corrosion; cracking although the brass has excellent migration resistance properties and is inexpensive. As to a phosphor bronze series alloy, although it has a sufficient mechanical strength and anti corrosion properties, it is not always satisfactory with respect to electric conductivity, the sensitivity to migration resistance and thermal resistance properties when it is used for a highly advanced electronic device. Further, a material made of phosphor bronze used for an electronic device is relatively expensive since it contains tin as the major component.